ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 903 



arsenic. " These slides were exhaustively tested agaiust the American 

 methods, viz. Dr. Chase's metallic silver and realgar, also Prof. 

 Smith's specimen slide. . . . The slide of Dr. Morris's sulphur and 

 arsenic combination gave the best results." 



Wax for Cells.* — Mr. C. M. Vorce recently found that while a 

 considerable number of cells in his collection had gone wrong, not one 

 of the wax cells or wax-bottomed curtain ring cells (described Amer. 

 Mon. Micr. Journ., i. (1880) p. 208) was found loose. 



Acting on the hint gathered from the durability of the wax cell 

 mounts the damaged slides were repaired in the following manner: — 

 The Atwood cells, and other loose cells having their covers still 

 attached, were cleaned of the old cement and the slip cleaned anew, 

 and placing the cell on a sheet of coloured wax, it was cut round with 

 a penknife, and, with the disc of wax adhering, transferred to the slip 

 and centered on the turntable, and slightly pressed to fix it in place. 

 The slip was then placed on the warming table and gently heated till 

 the wax slowly melted, when the excess exuded as a coloured ring 

 around the cell. The slide was then returned to the turntable, and a 

 ring of transparent cement spun around it over the wax. Gold size, 

 Bell's cement, liquid marine glue, Brown's rubber cement, or Folsom's 

 finishing cement, are all good for this purpose, and when dry the 

 slide is complete. 



In the case of loose covers, the top of the cell was cleaned of 

 cement by means of knife and turntable, a cover was selected or cut 

 of a size slightly smaller than the outer diameter of the cell, and 

 placed on the cell; warm (not melted) wax was then filled into the 

 space between cover and outer edge of cell by means of a knife-blade, 

 and finally smoothed by the same means on the turntable. Finishing 

 cement was then applied over the wax from inner edge of cell down 

 to and upon the slide, and the mount was complete. 



Mr. Vorce also writes, " My own experience leads me to conclude 

 that the condemnation of wax cells and the use of wax on account 

 of the sweating so common when it is used was premature. A wax 

 cell with a covering layer of cement, if used when freshly made, will 

 frequently sweat; but if well seasoned will scarcely ever sweat, 

 according to my experience. The wax appears to soften some 

 cements, probably because they contain some solvent of the wax, and 

 these will sweat no matter how old, unless years be allowed for 

 seasoning ; hence, cements containing turpentine or oil should not 

 be used for covering wax cells ; but benzole being so volatile will 

 wholly leave the wax in a few weeks, hence, as well as on account of 

 its colour, I generally employ Brunswick black. 



" The cells made as advocated in the article referred to have this 

 advantage, that the slide may be left (and freely used) with no other 

 cement than the primary wax filling around the edge of cover for 

 months or years, until it is seen whether any sweating will occur. If 

 it does occur, by placing the slide on a turntable the wax filling can 

 be instantly turned out with a sharp-pointed knife -blade, the cover 



* Amer. Mon. Micr. Journ., vii. (lSSti) pp. 123-4. 



